With a new mine plan finalised and several changes to various operating parameters already implemented, the Glencore-owned mine has been breaking its own production records over the last two months.
During October and November West Wallsend has consistently broken its own best production records. When mining of longwall block, LW23 began on 27 September 2000, the mine was 200,000t under the year to date annual budget. This was related to the challenges of mining a dyke in the earlier block LW22. In fact, according to operations manager Glen Lewis, there were at least three different operating regimes in LW 22 alone, including potential windblast conditions.
By the end of November, West Wallsend had caught up on its year to date annual budget of 2.786 Mt for 2000. During October the mine set new weekly and monthly production records. Best weekly production ever was 112,000t (previously 104,000t) while the best monthly figure, for October, was 410,000t (compared with an earlier record of 390,000t). In addition, during November the mine achieved a new shift record of 7804t, a new daily record of 25,974t, and a new weekly record of 120,000t. As at the end of November, the mine had set a new monthly record of 483,386 tonnes placing them 38,727 tonnes ahead of budget.
Lewis attributes the improvements to a combination of favourable mining conditions, improved operating standards and higher equipment utilisation as a result of a focused maintenance effort.
“For instance, the way our operators cut a full shear of coal has been changed,” Lewis said. “Now, on the first shear we take 60% of the 4.8m seam going to the main-gate and the other 40% going to the tail-gate, which has evened out the coal flow. Previously, we would flood the belt system going to the maingate by taking too much of the thick seam in the first pass. Improving and enforcing operating standards in the LW operation has assisted achieve the current results. All employees now see the benefit of high averages rather than high peaks.”
The new mine plan was developed as part of a Life-of-Mine study, began earlier in the year and is distinctly different to the previously approved 5 year plan for a number of reasons. Importantly, the mine has achieved about 50% better coverage of faults and structures by conducting an aeromagnetic survey, surface and in-seam drilling programs. In addition, more information has been collected in relation to potential face weighting and wind-blast conditions.
Significant changes in the mine plan will see an increase in block width from the current width of 140m to around 165m. LW26, (driveage in 2001, extraction in 2002) will be initially extended by 9m through the installation of five spare DBT chocks West Wallsend has on site. If the exercise proves successful, LW27 will be further extended.
The shearer speed will also be increased to around 8-9m/minute – currently running only between 25% to 30% full load current (7mpm). Lewis said the tailgate run is set at 50% (12mpm), indicating that operators can move at these higher speeds. To support this process, the face automation system, including horizon control, memory cut and chock initiation, is currently being activated and tested.
Adequate coal clearance remains one of the mine’s major production constraints and the system will undergo a significant upgrade, estimated to provide an additional 4000 tpd by allowing faster shearer speeds.
This will include an increase in drift capacity from 1,250tph to 2,600tph; trunk belts upgraded from 2,250 tph to 2,850 tph; longwall belt upgraded from 1,740 tph to 2,200 tph. It is intended to set breaker feeders in the development units to 200 tonnes per hr feed rate. Modified hoppers will allow high rate discharge from shuttle cars. The LW crusher rating is also to be upgraded to 3,000 tonnes per hour and the BSL rating to 3000 tonnes per hour peak.
The introduction of a weekend longwall and belt maintenance roster has provided an increase in operating hours of about 25% to 17 hours per day.
Lewis said the focus over the next few months will be on finalizing the upgrade contracts. Work is expected to commence on site early in 2001. For calendar 2001 West Wallsend is budgeted to produce 3.54 Mt.